The purpose of this research grant is to provide methodology for the isolation of human pancreatic carboxypeptidase B and human blood carboxypeptidase N. The study will give information on the active centers of both enzymes by using reagents already developed for bovine pancreatic carboxypeptidase B and will include an immunochemical study of both enzymes to determine the extent of structural homology. This information will help clarify the physiological importance of carboxypeptidase N as a kinase and anaphylatoxin inactivator in the blood of mammals.